One of critical issue with an AC coupling system is happening when battery has fully discharged.

There is no way to recover back.


So, I decide to install an addtional DC coupling

as below





Two panasonic HIT340 module on the shed at my back yard.


2 pannels are connected in series, it can generate 680W. (practically, it can generate 760~780W).





I have installed cheap MPPT charger,

Actually, this model can support 190V input, and working up to 160V.

When I make 2s 96cell module, Voc is around 130-140V. and Vmppt is around 120V.

It is too hard to use a generic 150V charger.

but, this MPPT controller is perfect in my case.





This is final connection,


I have installed 200W 48V to 12V DC2DC for Mini-computer (monitoring), NAS (Data storage & Web Server)

and Wireless Router (to keep on an in-house network).


whole system.png


I have installed 30kWh battery power


The useable capacity is around 24~25kWh. and, It is enough to supply 24 hours full power usage.

or 2-3 days limited power usage at my house.







The most people charge thier computer or smart phone frequently, and try to keep in full charge status.

They have to understand that is the worst habit to use a lithium chemistry.


When keep the high charge status over long time, battery degradation is happening.

Will lost capacity permanently, this damage can be increased with the temperature of battery (device).


This is why no one recommend do not keep charging all the time, to reduce the average status of charge.






I have 10kWh (51.2V, 200Ah) battery pack already.

But, it is not enough to back-up 2-3 days.

So, I have ordered custom battery pack module (total $6,000 include delivery/bus-bar box).

Each battery pack have 5kWh (51.2V, 100Ah) capacity.


Total 30kWh will enough

     2 days     without 0 solar production in winter season

     3 days     with 50% solar production in winter season

     unlimited  with 100% solar production in winter season


My power usage is around 12~16kWh in winter,  

The full solar production is just 10~13kWh in winter, I have to install an extra panels to support full power demand. and planing on this summer


     1.4kWAC panel for grid-tie, expected 2~3kWh extra in winter season

     0.7kWDC panel for battery back-up, expected 1kWh exra in winter season


Basically, no need to worry in spring/fall/summer, solar panel can generate more than a day amount.

just need a night back-up